The present disclosure relates to a developing device for supplying a developer to an image carrier and an electrophotographic image forming apparatus including the developing device.
In the electrophotographic image forming apparatus, an electrostatic latent image is formed by applying light based on image information read from an original-document image or on image information transmitted from an external device such as a computer with respect to a peripheral surface of an image carrier (photosensitive drum), and a toner image is formed by supplying toner from a developing device to the electrostatic latent image. After that, the toner image is transferred onto a paper sheet. The paper sheet after the transfer process undergoes a toner-image fixing process, and then is delivered to an outside.
By the way, in recent years, in image forming apparatuses, an apparatus structure has become more complicated in accordance with a transition to color printing and an increase in processing speed. In addition, in order to cope with the increase in processing speed, it is inevitable to rotate a toner stirring member in the developing device at high speed. In particular, in a developing method using a two-component developer containing magnetic carrier and toner, and using a magnetic roller (toner supplying roller) for carrying the developer and a developing roller for carrying only the toner, at a facing portion of the developing roller and the magnetic roller, only the toner is carried onto the developing roller by a magnetic brush formed on the magnetic roller, and further, toner that has not been used for development is peeled off from the developing roller. Therefore, suspension of toner is liable to occur in a vicinity of the facing portion of the developing roller and the magnetic roller. As a result, the suspended toner is deposited around an ear-cutting blade (regulation blade). When the deposited toner is aggregated and adheres to the developing roller, toner dropping may occur and cause image failures.
As a countermeasure, for example, there has been well-known the following developing device using a two-component developer containing magnetic carrier and toner, and using a magnetic roller for carrying the developer and a developing roller for carrying only the toner. That is, an air inlet hole for taking-in air from an outside of the developing device is provided through a wall portion facing the developing roller and the magnetic roller of a developing container, to thereby generate an airflow for causing the suspended toner around the ear-cutting blade to move upward.
Further, there has been well-known a developing device in which a thin plate is arranged between the developing roller and the toner supplying/collecting roller, the thin plate is brought into contact with the toner supplying/collecting roller through intermediation of a nonconductive member, and toner captured on the thin plate is collected onto the toner supplying/collecting roller by vibrating the thin plate and applying an alternating current.
Still further, there has been well-known a developing device including vibration means for vibrating an upper part of the developing roller in a frame body of the developing device. Yet further, there has been well-known a developing device including vibration means for vibrating a guide member for transporting a developer from the magnetic roller to the developing roller.